Wake steering via yaw control in multi-turbine wind farms: Recommendations based on large-eddy simulation

Abstract

The rotor area of a wind turbine must be perfectly perpendicular to the wind to deliver the most efficient performance as a single unit (i.e., yaw angle γ = 0°). When the rotor is misaligned (i.e., γ≠0°), the turbine power production is lower and greater structural loads may occur. However, a beneficial effect of yaw misalignment is that it steers the aerodynamic wake and, consequently, it may reduce wake losses for downstream wind turbines. To quantify and maximize such potential power gains while minimizing power losses, a wind farm with 28 wind turbines is investigated using large eddy simulations (LES). Selected turbines in the front-, mid-, and deep-rows are intentionally misaligned by positive (counter-clockwise) or negative (clockwise) yaw angles of various magnitudes. Consistent with previous studies, positive yaw misalignment angles cause net power gains, whereas negative ones cause net losses. We hypothesize that this is due to the Coriolis effect. Thus, only positive yaw misalignment angles should be considered for wake steering purposes in the northern hemisphere. Also, yawing front-row and deep-row turbines causes the overall power production to increase, while yawing mid-row turbines is not as effective. The most effective yaw misalignment angles are +20° for front-row and +10° for deep-row turbines.